Merge Pdfs

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations (openWorldHint, idempotentHint), the description adds the behavioral trait of preserving input order. It does not, however, disclose whether source files are modified, what happens to an existing output file, or how invalid/missing inputs are handled. With minimal safety-related annotations, this is a moderate gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single sentence with no filler; the core action and the key ordering constraint are front-loaded. Every word earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The schema and output schema cover most details, but the description leaves the mutually-required nature of source_urls/files_base64 ambiguous: both default to null, so an agent could invoke the tool without any input sources. Stating that at least one source array is required would close this meaningful gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, and the schema descriptions already explain output_name, source_urls, files_base64, and the ordering of inputs. The tool description adds no parameter-specific semantics beyond the schema, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource ('Merge multiple PDFs into a single PDF') and adds the ordering constraint, making it clearly distinct from siblings such as split_pdf, images_to_pdf, and rotate_pdf.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied by the purpose: use this when you need to combine PDFs. However, the description names no alternatives and gives no guidance on when to prefer source_urls over files_base64 or how to avoid conflicts with convert_file/images_to_pdf, leaving this to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.